diff --git a/demo/java-demo/src/main/java/com/alibaba/testable/demo/service/DemoPrivateAccessService.java b/demo/java-demo/src/main/java/com/alibaba/testable/demo/service/DemoPrivateAccessService.java
index fdd2f2d..336db49 100644
--- a/demo/java-demo/src/main/java/com/alibaba/testable/demo/service/DemoPrivateAccessService.java
+++ b/demo/java-demo/src/main/java/com/alibaba/testable/demo/service/DemoPrivateAccessService.java
@@ -7,6 +7,8 @@ public class DemoPrivateAccessService {
 
     private int count;
 
+    public final Double pi = 3.14;
+
     /**
      * private method
      */
diff --git a/demo/java-demo/src/test/java/com/alibaba/testable/demo/service/DemoPrivateAccessServiceTest.java b/demo/java-demo/src/test/java/com/alibaba/testable/demo/service/DemoPrivateAccessServiceTest.java
index f8c5b78..ae75d52 100644
--- a/demo/java-demo/src/test/java/com/alibaba/testable/demo/service/DemoPrivateAccessServiceTest.java
+++ b/demo/java-demo/src/test/java/com/alibaba/testable/demo/service/DemoPrivateAccessServiceTest.java
@@ -28,4 +28,10 @@ class DemoPrivateAccessServiceTest {
         assertEquals(new Integer(5), PrivateAccessor.get(demoService, "count"));
     }
 
+    @Test
+    void should_able_to_update_final_field() throws Exception {
+        demoService.pi = 4.13;
+        assertEquals(4.13, demoService.pi);
+    }
+
 }
diff --git a/demo/kotlin-demo/src/main/kotlin/com/alibaba/testable/demo/service/DemoPrivateAccessService.kt b/demo/kotlin-demo/src/main/kotlin/com/alibaba/testable/demo/service/DemoPrivateAccessService.kt
index 5ded99d..efca00c 100644
--- a/demo/kotlin-demo/src/main/kotlin/com/alibaba/testable/demo/service/DemoPrivateAccessService.kt
+++ b/demo/kotlin-demo/src/main/kotlin/com/alibaba/testable/demo/service/DemoPrivateAccessService.kt
@@ -8,6 +8,8 @@ class DemoPrivateAccessService {
 
     private var count = 0
 
+    final val pi = 3.14
+
     /**
      * private method
      */
diff --git a/demo/kotlin-demo/src/test/kotlin/com/alibaba/testable/demo/service/DemoPrivateAccessServiceTest.kt b/demo/kotlin-demo/src/test/kotlin/com/alibaba/testable/demo/service/DemoPrivateAccessServiceTest.kt
index d420599..05db7f1 100644
--- a/demo/kotlin-demo/src/test/kotlin/com/alibaba/testable/demo/service/DemoPrivateAccessServiceTest.kt
+++ b/demo/kotlin-demo/src/test/kotlin/com/alibaba/testable/demo/service/DemoPrivateAccessServiceTest.kt
@@ -20,4 +20,11 @@ internal class DemoPrivateAccessServiceTest {
         assertEquals("5", demoService.privateFieldAccessFunc())
         assertEquals(5, PrivateAccessor.get(demoService, "count"))
     }
+
+    @Test
+    fun should_able_to_update_final_field() {
+        PrivateAccessor.set(demoService, "pi", 4.13)
+        assertEquals(4.13, demoService.pi)
+    }
+
 }